The ballistic drive mechanism for the main gun of the Army's main battle tank is a complicated and precise mechanism. It includes tightly controlled electric and hydraulic servo-systems tied to a computer into which are fed a number of control variables such as target range, type of round, etc. The sighting mechanism is also complex to meet the requirements of operating safely within the armor of the vehicle and the ability to search out long range targets under conditions of restricted visibility, e.g. at night. Current sights may weigh between fifty and one hundred pounds and couple to the ballistic drive system with tolerances less than a thousandth of an inch.
Installing a sight and correlating it with its drive systems has proved to be very difficult. It may take as long as two hours for two or three men to mount the sight properly and much longer to synchronize it with the ballistic drive. The latter is generally accomplished for gun elevations from five degrees below horizontal to fifteen degrees above. Standard procedure is to position the fifty-seven ton vehicle on a vertically curved ramp and sight the target 1200 meters away through the gun barrel as the tank backs up the ramp. The tank stops at intervals while the tracking of the sight is checked and adjusted. If the sight fails to track, due to excessive backlash or the like, the ballistic drive mechanism arms are lengthened or shortened by screw and cam adjustments after which the whole procedure is repeated. The cost in time, manpower and energy is obviously excessive.